U.S. Pat. No. 3,642,728 teaches a new class of sulfonated polymers which are derived from polymers containing olefinic unsaturation, especially elastomeric polymers, e.g. butyl and ethylene-propylene terpolymers. These materials may be neutralized with organic amines or basic materials selected from Groups I, II, III, IV, V, VIB, VIIB and VIII and mixtures thereof of the Periodic Table of the Elements. These materials, especially the butyl and the ethylene-propylene terpolymer derivatives, may broadly be classified as thermoelastomers, that is these materials may be processed at high temperatures by use of shear force in the presence of selected polar additives and yet at the temperature of use, e.g. room temperature, the materials, through the association of the sulfonate group behave as cross-linked elastomers. Thus, these materials represent one form of reprocessable elastomers, which are very desirable in industry.
However, although these materials are commercially useful, the melt viscosity even at very high temperature tends to be sufficiently high as to preclude the use of conventional plastic fabrication techniques. Thus, the very purpose for which these compounds are derived is not adequately fulfilled. In this invention, it has unexpectedly been discovered that decreased melt viscosity may be obtained by combining these polymers with a minor portion of a crystalline polyolefin in a polymer blend. Further, it has been unexpectedly discovered that the physical properties of these blends, as measured at room temperature, can be substantially improved as compared to the sulfonated elastomers alone.
The sulfonated elastomers described in U.S. Pat. No. 3,642,728 when used as gums possess a relatively low level of rigidity or stiffness which yields rather limp materials incapable of supporting themselves when prepared in thin sections. This is a major limitation, if one desires to prepare dimensionally stable parts, e.g. automotive or appliance applications. It is known in the art that stiffness of elastomers may be increased by the combination of carbon black or inorganic material such as clays, calcium carbonate or silicates, etc. However, these materials, while increasing the hardness, further deteriorate the melt viscosity of the above-described ionic elastomers. Thus, systems which at best have borderline processability even at very low metal sulfonate levels further deteriorate in their flow behavior and thus cannot be processed at all. It has unexpectedly been discovered that the compositions of the instant invention wherein minor amounts of the crystalline polyolefin are combined with the sulfonated elastomers described above result in increased stiffness at room temperatures.
Thus, this invention teaches compositions of matter which represent significant improvement over the prior art in that low melt viscosity is obtained at no loss in physical properties and, in fact, a gain in physical properties is realized.